This invention relates to a solvent absorption process for the separation of a mixed gas. More particularly, it relates to a process for separating a mixed gas by utilizing the differences in solubility of its constituents in a solvent.
Conventionally, a solvent absorption process for the separation of a mixed gas is well known as one of the processes for treating of waste gas containing radioactive components as discharged from atomic energy facilities including nuclear reactors or waste gas containing harmful components as released from a variety of plants. In this process, carbon tetrachloride CCl.sub.4, various types of Freon (the trade name of fluorocarbons manufactured and sold by E. I. du Pont de Nemours & Co. Inc.) such as dichlorodifluoromethane CCl.sub.2 F.sub.2 (Freon 12), etc. have been employed as the solvent for absorbing the gas. However, these solvents have the disadvantage of undergoing degradation upon exposure to radiation and thereby producing corrosive detrimental materials such as chlorine gas. Moreover, they are apt to vaporize during the gas separating operation due to their high vapor pressures, thus requiring a condenser for recovering the vaporized solvent. Particularly, Freons have a boiling point that is too low for a gas separating operation at ordinary temperatures.
In Table I below are shown the physical properties of some solvents heretofore in use and the solubilities of various gases in these solvents.
Table I __________________________________________________________________________ Data on Some Prior Art Solvents __________________________________________________________________________ Tempera- Vapor Boiling Solubility Solubility ture Pressure Point (molor fraction) Ratio Solvent (.degree. C) (mmHg) (.degree. C) N.sub.2 Ar Kr Xe (Kr/N.sub.2) __________________________________________________________________________ Carbon tetra- 25 105 76.7 6.3 1.1 3.1 1.3 4.92 chloride .times.10.sup.-4 .times.10.sup.-3 .times.10.sup.-3 .times.10.sup.-2 Freon 12 0 2400 -30 2.01 -- 10.6 3.31 5.32 .times.10.sup.-3 .times.10.sup.-3 .times.10.sup.-2 Freon 0 135 47.7 2.4 -- 8.5 2.65 3.54 113 .times.10.sup.-3 .times.10.sup.-3 .times.10.sup.-2 Toluene 25 &lt;1 110.8 2.1 -- 8.8 2.5 4.19 .times.10.sup.-3 .times.10.sup.-3 .times.10.sup.-2 __________________________________________________________________________